Installation issue: python build errors on windows

[clintonstimpson]

Steps to reproduce the issue

$ spack spec -I
 -   vsnhnyf  python@3.12.13+bz2+ctypes~dbm~debug+libxml2+lzma~optimizations+pic+pyexpat~pythoncmd~readline+shared+sqlite3+ssl~static~tests~tkinter+uuid+zlib build_system=generic platform=windows os=windows10.0.26200 target=alderlake %c,cxx=msvc@19.51.36248
[+]  c6j2ped      ^compiler-wrapper@1.0 build_system=generic platform=windows os=windows10.0.26200 target=alderlake
[e]  khc53ll      ^msvc@19.51.36248 build_system=generic platform=windows os=windows10.0.26200 target=x86_64

I'm using Visual Studio 2026.

Error message

Error message

> C:\Program Files\Microsoft Visual Studio\18\Professional\MSBuild\Microsoft\VC\v180\Microsoft.CppBuild.targets(473,5): error MSB8020: The build tools for Visual Studio 2015 (Platform Toolset = 'v140') cannot be found. To build using the v140 build tools, please install Visual Studio 2015 build tools.  Alternatively, you may upgrade to the current Visual Studio tools by selecting the Project menu or right-click the solution, and then selecting "Retarget solution". [C:\Users\cjstimp\.spack\stage\python-3.12.13-vsnhnyf\spack-src\PCbuild\_freeze_module.vcxproj]



> Build FAILED.

Information on your system

from config in Spack v1.2.

• Spack: 1.3.0.dev0 (spack/spack@b495c19)
• Builtin repo: ...\spack-packages\repos\spack_repo\builtin (95b32de)
• Python: 3.12.10
• Platform: windows-windows10.0.26200-alderlake

Additional information

@adamjstewart @scheibelp

General information

• I have run spack debug report and reported the version of Spack/Python/Platform
• I have run spack maintainers <name-of-the-package> and @mentioned any maintainers
• I have uploaded the build log and environment files
• I have searched the issues of this repo and believe this is not a duplicate

[adamjstewart]

@johnwparent

[johnwparent]

Python 3.12.13 was built targeting Vs22, Vs26 will complain about an upgrade when given an old msbuild file.
At one point I had support for migrating from vs17 to vs22 but that a. doesn't apply here, and b. has clearly slipped from the Python recipe.

Should be a fairly reasonable solve, thanks for trying Spack on Windows!

[johnwparent]

Actually was an issue with the MSVC compiler just not being updated to support VS26. A larger rework, but I can unblock this issue quickly.